1. Field of the Invention
The present invention relates generally to a private branch exchange apparatus and accounting process method used in an office, a business branch, etc., and more particular to a private branch exchange wherein an accounting process is executed on a calling-side extension when a call is made from an extension to an outside line.
2. Description of the Related Art
In general, a currently used private branch exchange apparatus has various service functions. One of the service functions is an accounting process function. The accounting process function has a memory table and timer, The memory table is registered identification number information indicative of communication service providers, and information indicative of call charges associated with the identification number information. When a call is sent from an extension to an outside line, an accounting process function executes accounting process on the basis of the registered content of the memory table and a difference between a call beginning time and a call end time measured by the timer.
In this type of private branch exchange apparatus, the timer needs to be re-set for various reasons. As a result, an accounting calculation result relating to a call made during the time in which the timer is re-set may differ from an accounting calculation result relating to the actual call time. In order to solve this problem, there is a method wherein when the time of the timer has been changed, call beginning times of all existing calls, which are managed by the private branch exchange apparatus, are rewritten in a batch.
In this method, however, a CPU executes a process relating to calls, a batch-rewrite process for call beginning times and an accounting calculation process for call-sending extensions. Thus, the processing load of the CPU increases, and a predetermined time is needed for the batch-rewrite of call beginning times due to the change of time. When the rewriting work is performed at the time of the end of calls, a serious problem arises with the execution of the accounting calculation process.